Details
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Bug
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Status: Closed (View Workflow)
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Major
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Resolution: Fixed
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5.5(EOL), 10.0(EOL), 10.1(EOL)
Description
This script:
DROP TABLE IF EXISTS t1;
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CREATE TABLE t1 (a INT);
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INSERT INTO t1 VALUES (10),(11),(12);
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EXPLAIN EXTENDED SELECT * FROM t1 WHERE a=10 AND IF(a=10,1,0)=1;
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SHOW WARNINGS;
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returns
+-------+------+-----------------------------------------------------------------------------+
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| Level | Code | Message |
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+-------+------+-----------------------------------------------------------------------------+
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| Note | 1003 | select `test`.`t1`.`a` AS `a` from `test`.`t1` where (`test`.`t1`.`a` = 10) |
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+-------+------+-----------------------------------------------------------------------------+
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I.e. the field equal value of 10 was propagated into IF, then the condition part with IF was evaluated as a constant and removed from the condition.
If I use VARCHAR in the same scenario:
DROP TABLE IF EXISTS t1;
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CREATE TABLE t1 (a VARCHAR(10));
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INSERT INTO t1 VALUES ('10'),('11'),('12');
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EXPLAIN EXTENDED SELECT * FROM t1 WHERE a='10' AND IF(a='10',1,0)=1;
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SHOW WARNINGS;
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it returns:
+-------+------+----------------------------------------------------------------------------------------------------------------------------+
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| Level | Code | Message |
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+-------+------+----------------------------------------------------------------------------------------------------------------------------+
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| Note | 1003 | select `test`.`t1`.`a` AS `a` from `test`.`t1` where ((`test`.`t1`.`a` = '10') and (if((`test`.`t1`.`a` = '10'),1,0) = 1)) |
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+-------+------+----------------------------------------------------------------------------------------------------------------------------+
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Propagation did not work.
Tracing in gdb shows the following:
(gdb) b Item_field::subst_argument_checker(unsigned char**)
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Breakpoint 3 at 0x555555c46d98: file /home/bar/maria-git/server/sql/item.cc, line 5361.
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(gdb) c
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Continuing.
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Breakpoint 3, Item_field::subst_argument_checker (this=0x7fff9c007f70,
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arg=0x7fffd9f04a00) at /home/bar/maria-git/server/sql/item.cc:5361
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5361 return *arg &&
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(gdb) p (Subst_constraint) *arg
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$3 = Item::IDENTITY_SUBST
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I.e. Item_field::subst_argument_checker() is called with a wrong Subst_constaint value.
The correct value should be Item::ANY_SUBST, because the field appears in a comparison context.
Attachments
Issue Links
- blocks
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- Closed
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Activity
| Field | Original Value | New Value |
|---|---|---|
| Summary | Equal fields propagations is not used for VARCHAR when it safely could | Equal fields propagation is not used for VARCHAR when it safely could |
| Summary | Equal fields propagation is not used for VARCHAR when it safely could | Equal field propagation is not used for VARCHAR when it safely could |
| Fix Version/s | 10.1.7 [ 19604 ] | |
| Fix Version/s | 10.1 [ 16100 ] | |
| Resolution | Fixed [ 1 ] | |
| Status | Open [ 1 ] | Closed [ 6 ] |
| Labels | propagation |
After the fix this script in MariaDB:
DROP TABLE IF EXISTS t1;
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CREATE TABLE t1 (a VARCHAR(10));
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INSERT INTO t1 VALUES ('10'),('11'),('12');
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EXPLAIN EXTENDED SELECT * FROM t1 WHERE a='10' AND IF(a='10',1,0)=1;
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SHOW WARNINGS;
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returns
+-------+------+-------------------------------------------------------------------------------+
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| Level | Code | Message |
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+-------+------+-------------------------------------------------------------------------------+
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| Note | 1003 | select `test`.`t1`.`a` AS `a` from `test`.`t1` where (`test`.`t1`.`a` = '10') |
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+-------+------+-------------------------------------------------------------------------------+
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MySQL-5.7.8 does not support propagation in the same scenario:
+---------+------+-------------------------------------------------------------------------------------------------------------------------------------------+
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| Level | Code | Message |
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+---------+------+-------------------------------------------------------------------------------------------------------------------------------------------+
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| Warning | 1681 | 'EXTENDED' is deprecated and will be removed in a future release. |
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| Note | 1003 | /* select#1 */ select `test`.`t1`.`a` AS `a` from `test`.`t1` where ((`test`.`t1`.`a` = '10') and (if((`test`.`t1`.`a` = '10'),1,0) = 1)) |
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+---------+------+-------------------------------------------------------------------------------------------------------------------------------------------+
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| Labels | propagation | propagation upstream |
| Workflow | MariaDB v3 [ 71216 ] | MariaDB v4 [ 149516 ] |
Another example:
DROP TABLE IF EXISTS t1;CREATE TABLE t1 (a VARCHAR(10));INSERT INTO t1 VALUES ('10'),('11'),('12');EXPLAIN EXTENDED SELECT * FROM t1 WHERE a='10' AND CASE WHEN a='10' THEN 1 ELSE 0 END;SHOW WARNINGS;returns:
+-------+------+--------------------------------------------------------------------------------------------------------------------------------------------+| Level | Code | Message |+-------+------+--------------------------------------------------------------------------------------------------------------------------------------------+| Note | 1003 | select `test`.`t1`.`a` AS `a` from `test`.`t1` where ((`test`.`t1`.`a` = '10') and (case when (`test`.`t1`.`a` = '10') then 1 else 0 end)) |+-------+------+--------------------------------------------------------------------------------------------------------------------------------------------+Equal fields propagation did not work.
The expected result is:
+-------+------+-------------------------------------------------------------------------------+| Level | Code | Message |+-------+------+-------------------------------------------------------------------------------+| Note | 1003 | select `test`.`t1`.`a` AS `a` from `test`.`t1` where (`test`.`t1`.`a` = '10') |+-------+------+-------------------------------------------------------------------------------+